The growing subfield of infant and early childhood temperament holds great promise for conceptualizing the individual's contribution to social and cognitive development; however, the field is handicapped by insufficient basic psychometric research and inadequately standardized and validated measurement instruments. The goal of this research is to validate a novel, theoretically based method for measuring temperament- related behavior: The Laboratory Temperament Assessment Battery (LAB- TAB). LAB-TAB yields scores for activity, fear, anger, pleasure, and interest from objectively scored standardized laboratory measures. The assessment procedure will be extended to younger infants. Six validity studies examine developmental continuity, cross-method convergence, and relations between facial expressions and overt behavioral responses. Other validity studies demonstrate the relevance of temperament to various facets of social development. Issues addressed include prenatal efforts to socialize infant temperament, the role of temperament in emotional communication, and the role of temperament in instigating behavior. Both cross-sectional and longitudinal approaches are used. The health relatedness of the research derives from the proposition that early temperament is implicated in the etiology of various childhood behavioral problems. Successful implementation of LAB-TAB should improve understanding of factors within the child that either contribute to vulnerability or protect the child from stressful environmental influences.